Kamal Has a Free API That Deploys Docker Apps Without Kubernetes

#kamal #docker #deployment #devops

Kamal (from Basecamp/37signals) deploys Docker containers to any server. No Kubernetes. No cloud vendor lock-in. Just SSH and Docker.

config/deploy.yml

service: scraping-app
image: username/scraping-app

servers:
  web:
    - 192.168.1.100
    - 192.168.1.101
  worker:
    hosts:
      - 192.168.1.102
    cmd: node worker.js

registry:
  server: ghcr.io
  username: username
  password:
    - KAMAL_REGISTRY_PASSWORD

env:
  clear:
    NODE_ENV: production
    PORT: 3000
  secret:
    - DATABASE_URL
    - API_KEY

traefik:
  options:
    publish:
      - "443:443"
    volume:
      - "/letsencrypt:/letsencrypt"
  args:
    entryPoints.websecure.address: ":443"
    certificatesResolvers.letsencrypt.acme.email: "admin@example.com"
    certificatesResolvers.letsencrypt.acme.storage: "/letsencrypt/acme.json"

accessories:
  db:
    image: postgres:16
    host: 192.168.1.100
    port: 5432
    env:
      clear:
        POSTGRES_DB: scraping
      secret:
        - POSTGRES_PASSWORD
    volumes:
      - /var/lib/postgresql/data:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine
    host: 192.168.1.100
    port: 6379

Deploy Commands

# First deploy — sets up everything
kamal setup

# Deploy new version
kamal deploy

# Rolling restart (zero downtime)
kamal app boot

# View logs
kamal app logs
kamal app logs --follow

# Run command on server
kamal app exec 'node scripts/migrate.js'

# Console access
kamal app exec -i 'node'

Zero-Downtime Deploys

Kamal uses Traefik as a reverse proxy. New container starts → health check passes → traffic switches → old container stops. Zero downtime.

Secrets Management

# Set secrets from .env
kamal env push

# .env file
KAMAL_REGISTRY_PASSWORD=ghp_xxx
DATABASE_URL=postgres://user:pass@db:5432/scraping
API_KEY=sk-xxx

Multi-App Deploy

# Deploy web + worker + cron
servers:
  web:
    - 192.168.1.100
  worker:
    hosts: [192.168.1.101]
    cmd: node worker.js
  cron:
    hosts: [192.168.1.101]
    cmd: node cron.js